Mixing machine



5- L. GOODCH ILD MIXING MACHINE April 4, 1950 4 Sheets-Sheet 1 Filed Nov. 28, 1945 [men for Syn/YE) Lnogc/vcz Goaocmo Attorney s April 1950 s. GOODCHILD 2,502

MIXING MACHINE I Filed Nov. 28, 1945 4 Sheets-Sheet 2 Inventor 4'4 firm/Er LAURENCE 6000011140 Mefirk After hey:

AP 4, 1950 s. GOODCHILD 2,502,563

MIXING MACHINE Filed Nov. 28, 1945 4 Sheets-Sheet 3 In renter nwuwcz 6000 CHILD April 4, 1950 5.1.. GOODCHILD 2,502,563

MIXING MACHIljE Filed No,v 28, 1945 4 Sheets-Sheet 4 flu en to?" Jxa/ve'y 11mm: Goons/ma Attorneys Patented Apr. 4, 1950 Sydney Laurence Goodchild, Beckenham,

, England f Application November 28, 1945, Serial No. 631,296 In Great Britain December 7, 1944 Y 8 Claims. (01. 259-104) 1 This invention relates to machines for mixing and kneading plastic masses and more particularly for incorporating and dispersing pigments into oils, resins, varnishes, cellulose and other plastics and subsequently reducing the pigmented,

plastic thus formed with solvents, paint media, etc. into a uniform flowable paste or liquid. Oi known machines of this kind, kneaders or internal mixers of the Werner Pfleiderer or Banbury type have had a certain amount of success but these,

machinesv suffer from the following disadvantages? 1..The volume of material for mixing action in the stifi state is critical. 2. The material mixed tends to be thrown out of the mixing chamber needing hydraulic rams, etc. to return it. 3. The mixing action is not entirely positive if the charge is sticky, and when solvent is added to reduce the mass, the charge slips and pro-- longed mixing is required to incorporate the solvent. 4. When being reduced with solvent, the mass sticks to the sides of the vessel and the back of the rotors, and it is difficult to produce a uniform smooth paste with good dispersion of the pigment.

Most success has been obtained in the dispersion of pigments into cellulose plastics, but to reduce the-plastic for use it is usual, in order to over come the above difliculties, to empty the charge and sheet the pigmented plastic over roller mills, to dry this sheet free of solvent, and then to breakit up into chips. These chips are subsequently dissolved in a vortex mixer in solvents, and it will thus be seen that several machines and stages are required. In the case of concentrated plastics of pigment in oil, varnish or synthetic resin, no quick and easy method of reducing the paste without flocculation of the pigment exists.

1- 'The principal object of the present invention is to provide an apparatus for the production of fiowable pastes or liquids from pigment and media without the difficulties described above,- and which makes available paints and compositions of high pigment content and good gloss and dispersion.

' According to the invention, a machine for the purpose specified comprises a mixing chamber and one or more members which are adapted for rotation therein in such manner that the material under treatment is positively mixed and kneaded while each of the surfaces of said rotatable members and of said chamber which contacts the material under treatment, is contacted, wiped or narrowly cleared by one or other of the remainder ofusaid surfaces.

machine comprises a closed chamber of a shape equivalent to two parallel, intersecting cylinders within which are disposed, with a narrow clearance, two pairs of oppositely rotatable, intermeshing rotors, the rotors of each pair being located one in each part-cylindrical portion of th chamber and being of such shape that the periphery of one is contacted, wiped, or narrowly cleared by the periphery of the other. The pairs of rotors desirably rotate at different speeds since such diiferential movement assists homogeneous mixing. In this case, the rotors have a lateral width inversely proportional to the speed at which theyare rotated, in order that the two pairs of rotors shall have the same displacement. The

rotor teeth consist of epiand hypocycloidalv curves.

According to another embodiment, a chamber as above described contains only one pair of intermeshing rotors which are, however, less wide than the chamber so that the charge is exuded laterally into a free space. To ensure that the two sides of the chamber are contacted and wiped, and the whole charge worked upon, the rotors are adapted to be given a to and fro lateral action within the chamber. The rotor teeth are helical and, as in the previous embodiments, are of epiand hypocycloidal form and their direction of rotation can be reversed in synchronism with the reversal of the lateral stroke.

According to yet another embodiment, the chamber is rotatable and consists of a cylinder, the inner periphery of which is toothed, with epiand hypocycloidal teeth. An inner rotor with a, small number of teeth engages the teeth of.

the chamber. and a crescent-shaped abutment fills the space not covered by the path of the teeth.

As in the previous embodiment, the internal rotor is less wide than the cylinder in order to give the charge a path to the suction side of the mixing cycle and is given a similar lateral action.

In any of the embodiments, above described,

I I some of the rotor teeth may be omitted, the rotors chamber in which the rotors are-adapted to work,-

'.'-.Acc0rding to the preferred embodiment, the

Figure 3 is a plan view of the complete machine,

Figure 4 is a side elevation corresponding to Figure 3, partly in section on the line AA,

3 Figure 5 is an enlarged section on the line AA of Figure 3,

Figure 6 is a section on the line VIVI of Pi ure 5, and,

Figures 7, 8 and9 are detail views;

The mixing chamber consists of upper and lower members In and H secured together by. means of vertical bolts 12, and side members ll which are secured to members l and l I bymeans; of horizontal bolts I6 and to the foundation. l

by means of foot bolts ll. The chamber l8 thus formed is in the shape of two intersecting cylinders as shown more particularly. in Eiguresfl. and:

6. Two pairs of rotors a, b, and cr, y are located"- within the chamber I8, the pair ab being driven. in the opposite direction to the pair any. As shown, a. and :c are being driven in the clockwise direction, while b and y are being driveniin the counter-- clockwise direction, but such; relative directions of"rotation, may-be reversed as explained hereinafter.. Rotors a' andbare secured to parallel shafts i9 and 20,. and rotors IL and y are secured to parallel shafts 2! and 22; Sideplay inthe shafts |922 is limited by thrust bearings 23' which bear against the side face of the outer bearing on each rotor shaft; Combined bearings and spring-loaded glands 24 tend to force the rotors together, the outerdiameter of theglands being sealed with packing, but are resisted bythe bearings 23 so that" in practice there is a small lateral clearance between the rotors; tors, are of such shape that" the whole of the periphery'of one is contacted; wiped or narrow- 1y cleared b the periphery of the mating-rotor; and as shown the rotors are formed with six teeth 25 consisting of epicycloidal and'hypocycloidal curves. Other numbers. of teeth may be employed; Generally; theclearancebetween the rotors, and between the rotors'and the Wall of the chamber, is of theorder ofa few thousandths of an inch, but for bigmachines'or for operating on special plastics, clearances of up to the order of a quarter of an inch between the rotors may be employed. It will thusbe: appreciated that'no sticky masses-can permanently-adhere to the rotors or to the wall of "the mixing-chamber.

Material is fed' to the chamber through an opening 26 normally closed by a removable charge plug 26a and enters the chamber substantiall at'a tangent to the rotor b so-that the material is drawn in when 17 is rotating anticlockwise. The material is then carried downwards around rotor buntil' it reaches thezone immediately below the line" along which the rotors a' and b intermesh. Here the material is kneaded and forced to pass laterally along'the teeth ofrotors ab to the rear pair of rotors xy which, rotating in the opposite direction, pass itupwardly-round the rotor-spacesto a zone immediately above the line along which'rot'orsmy intermesh, whence it is, forced laterally into the spaces of the front rotors ab, thus completing a mixing cycle. Once the charge has been introduced, it will be appreciated that. the relative-rotation of the pairs of rotors may bereversed one or more times during the mixing operation to ensure homogeneous mixing. The twopairs of rotors preferably rotate at difierent speeds; thus giving differential" movement" to aid homogeneous mixing, and in this case, toensurethat 'thetwo sets of rotors shall have the same displacement; the rotors have a lateral width inversely proportional to their rotational speeds. Thus, in the. embodiment shown, rotors xy rotate at a higher speedthan-rotorsub';

The ro- Tubular channels 21 are formed in the members II) and H for the passage of a cooling medium, usually water. The supply and return of the cooling medium is, eifected through cover plates 28 having a single water inlet:29.

Shafts [9 to 22 are supported in suitable bearings 3B and when the machine is mixing, said shafts are normally driven from the common shaft 31jby means of the fast pulley 32. The provision of two loose pulleys 33 and crossed and open belts (not shown) allows for a main drive in either direction. Shafts l9 and 20 with their associatedirotors ab are driven from the shaft 3| by means of the spur wheels 34 and 35 and pinions, 36,, whileshafts 2| and 22 with their associated rotors my are driven from the shaft 3| by means of the spur wheels 31 and 38 and pinions 39. It will thus be seen that the pairs of rotors aband my are driven in opposite rotational die rections by the common shaft 3 I. While the mix ing; chamber is being charged, the rotors are driven in the direction shown in Figure 1, but

during the mixing operation, the directions 0t.

rotation can be changed intermittently by re versingthe direction of rotation of shaft 31' by Slipping in either the crossed or open belt as the case may be.

At' the completion ofthe mixing operation,

when it is required to empty the mixing chamber; shaftSl is pushed horizontally tothe left thus throwing spur wheels 34 and 35 out of engage ment while retaining engagement between spur wheels 31 and 38 as will be seen from Figure 3; Gear wheels 40 and M carried b -layshaft 42 are then brought into engagement with the driving pinions 39 and 36 respectively, thus reversing the direction of rotation of the rotors ab. Thebears ings 43"for layshaft 42 are mounted on slides-s0 that wheels 40 and 4| can be thrown compl'ete l'y out of engagement with the pinions when not required for empt ing. When set for emptying; rotors b and a should rotate in an anticlockwise direction and rotors a and y in a clockwise direction, thus forming in effect a gear type pump which willforce out the cont'entsthrough the discharge orifice 44 normally closed by plug 45; It will thusv be understood that the wheels 40 and 4| will be brought in while shaft 3| i's rotating in the directionsuch that the-rotors are rotating in the opposite directionsto those shown in-Figure 1.

The machine may be thoroughly cleaned by slackingoff the retaining springs and" sliding glands 24'clear onto the reduced portions'ofthe shafts l9-22. The sides M of the mixing chamber may then be slid toleft and right by remov ing the horizontal bolts I6 and the foot bolts l1. By'removing verticalbolts 12 the two halves I ll and II of; the rotorhousing may-be taken apart and thoroughly cleaned. The upper half may be removed directly, the lower half then being dropped into the well 46 and brought forward;

The faces between the two pairs of rotors may be cleaned by slightly separating the rotors lat erally. The rotors themselves are not removed from the machine for cleaning, as they'are-completely exposed oncethe rotor casing and sides have been removed.

It; will be: appreciated: that as the movement of" the charge is positive; kneading and mixing will take place even though the free space in-the machine is only partly occupied, and that the machineneedzonlysbe partly loadedwith pigment and media to give a stiff plastic, with thearesult that spa-eels available forthe; additionof solvent or more medium for reducing purposes. The

machine will therefore operate effectively at allv stages.

The rotors as shown are all of the same diameter and have the same number of teeth but I do not wish to limit myself to this arrangement and the mating rotors may have different num.

bers of teeth, and the pairs may differ from each other in diameter and/or number of teeth provided that, relative speeds of rotation and width pair of rotors is substantially the same and that the point of kneading displacement is approximately laterally opposite the suction zone of theother pair of rotors.

1o considered, the volumetric displacement of each The machine according to the present mven I tion has several advantages over known ma-I' chines. Thus, paints of high gloss can be produced more easily than hitherto due to thegood of each pair in each part-cylindrical portion 01' the chamber with a narrow clearance between said rotors and respective cylinder walls, so shaped that the entire periphery of one rotor of each pair is narrowly cleared in motion by the entire periphery of the other rotor of the pair and each pair of rotors having a lateral width inversely proportional to the rotational speed of the rotors.

3. A mixing device for the purpose described comprising a closed mixing chamber of a shape equivalent to two parallel intersecting cylinders, inlet and outlet means in said chamber, two oppositely rotatable pairs of intermeshing toothed rotors, said teeth on said rotors consisting of epiand hypocycloidal curves, and means for rotating said pairs of rotors at difierent speeds, said rotors being disposed one of each pair in each part- -cylindrical portion of the chamber with a narrow clearance in between said rotors and respective gcylinder Walls, and said rotors being so shaped that the periphery of one rotor of each pair is lnarrowly cleared by the periphery of the other rotor of the pair, the lateral width of each pair of rotors being inversely proportional to the respective rotational speeds.

4. A mixing device for the purpose described comprising a closed mixing chamber of a shape This operation is diflicult in existing mixers: be-

cause of slipping of the semi-solid massin 'the mobile aqueous media. In further amplification of the second embodiment the machine comprises a closed mixing chamber similar to that ofthe preferred embodiment consisting of members 10, ll, [2, I4, I5, l6, l1, Figs. 2, 3 and 6, This chamber contains one pair of intermeshing rotors struction, of helical form, and are less wide than the chamber. The charge being worked is forced axially along the teeth into a free space at the end of the rotors. To ensure that each side of the mixing chamber and rotors be wiped and the whole charge worked upon a lateral action is imparted to the rotors. This action is produced by cams acting on each rotor shaft. Rotors; and cams are driven through gearing by a reversible electric motor. The cams are arranged to. pro- .vide a dwell at the end of each stroke and in addition to operate a switch which first stops and then reverses the drive.

I claim:

1. A mixing device for the purpose described comprising a closed mixing chamber of a shape equivalent to two parallel intersecting cylinders, inlet and outlet means in said chamber and two oppositely rotatable pairs of intermeshing toothed rotors, said rotors being disposed one of each pair in each part-cylindrical portion of the chamber with a narrow clearance between said rotors and respective cylinder walls and said rotors being so shaped that the entire periphery of one rotor of each pair is narrowly cleared in motion by the entire periphery of the other rotor of the pair.

2. A mixing device for the purpose described comprising a closed mixing chamber of a shape equivalent to two parallel intersecting cylinders, inlet and outlet means in said chamber, two oppositely rotatable pairs of intermeshing toothed rotors, and means for rotating said pairs of rotors at difierent speeds, said rotors being disposed one '40 which are of epicycloidal and hypocycloidal conequivalent to two parallel intersecting cylinders, inlet and outlet means in said chamber, two oppositely rotatable pairs of intermeshing toothed rotors, said teeth on said rotors consisting of epiand hypocycloidal curves, and a common driving shaft for driving said pairs of rotors at different speeds, said rotors being disposed one of each pair in each part-cylindrical portion of the chamber with a narrow clearance in between said rotors and respective cylinder walls, and said rotors being so shaped that the periphery of one rotor of each pair is narrowly cleared by the periphery of the other rotor of the pair, the lateral Width of each pair of rotors being inversely proportional to the respective rotational speeds.

5. A mixing machine according to claim 4 further comprising additional means for reversing the direction of rotation of one pair of rotors and means for bringing said reversing means into operation when said driving shaft is rendered inoperative with respect to said pair of rotors.

6. A mixing machine according to claim 4 further comprising means for rotating the common driving shaft in either direction.

7. A mixing device according to claim 1 further comprising a discharge means in said chamber located in a position immediately below the line along which the rotors intermesh.

8. A device according to claim 1 wherein the said inlet is arranged on one side of the chamber so that the material, on entry, contacts a toothed rotor at a substantial tangent.

SYDNEY LAURENCE GOODCHILD.

REFERENCES CITED M The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 68,101 Mills Aug. 27, 1867 1,424,445 Bowen et al Aug. 1, 1922 FOREIGN PATENTS Number Country Date 552,515 Great Britain Apr. 12, 1943 760,614 France Feb. 27, 1934 

